The present invention relates to an apparatus for fluidizing, degassing and pumping a suspension of fibrous cellulose material.
Apparatuses for fluidizing, degassing and pumping pulp of medium consistency are known through U.S. Pat. No. 4,410,337 and U.S. Pat. No. 4,435,193 (corresponding to SE 8102118-0). The apparatuses described therein comprise a housing, a fluidizing rotor and an impeller of radial type axially aligned with the rotor, said housing comprising a cylindrical portion for the rotor, a portion for the impeller, said portion being radially enlarged in relation to the cylindrical portion, a wall closing one end of the housing and a shaft extending through the wall and being rigidly connected to the impeller. The housing is provided with an axial inlet for suspension at the cylindrical portion, a radial outlet for suspension at the radially enlarged portion and a degassing system for removing gas collecting in front of the impeller and comprising openings in the impeller and the wall, said impeller having a hub, a partition surrounding the hub and a plurality of forward blades facing said axial inlet of the housing, and a plurality of rear blades facing away from said axial inlet, said forward and rear blades being rigidly connected to the partition. The purpose of the rear blades is only to separate pulp which may have accompanied the gas flow through a plurality of small openings in the partition which is formed as a plate. These small openings have a total through-flow area which is too small to supply any controlled, large quantity of pulp to the rear blade space, neither are they located at such a radial distance from the central axis that pulp can flow through them in a controllable manner, i.e. the openings are located within the radial extension of the gas bubble during normal operation, solely in order to be included in the degassing system. Furthermore, the rear blades have considerably smaller width than the forward blades, which further indicates that they are not intended to exert a pump action on any continuously supplied pulp. The known apparatuses have satisfactory performance with respect to all functions, but improvement is nevertheless desirable.